Fix buildUrl annotation in kokoro job (#27105)

tools/internal_ci/linux/grpc_e2e_performance_v2.sh

@@ -38,6 +38,7 @@ fi
 BIGQUERY_TABLE_8CORE=e2e_benchmarks.experimental_results
 BIGQUERY_TABLE_32CORE=e2e_benchmarks.experimental_results_32core
 # END differentiate experimental configuration from master configuration.
+CLOUD_LOGGING_URL="https://source.cloud.google.com/results/invocations/${KOKORO_BUILD_ID}"
 PREBUILT_IMAGE_PREFIX="gcr.io/grpc-testing/e2etesting/pre_built_workers/${LOAD_TEST_PREFIX}"
 UNIQUE_IDENTIFIER="$(date +%Y%m%d%H%M%S)"
 ROOT_DIRECTORY_OF_DOCKERFILES="../test-infra/containers/pre_built_workers/"
@@ -79,7 +80,7 @@ buildConfigs() {
         -s prebuilt_image_prefix="${PREBUILT_IMAGE_PREFIX}" \
         -s prebuilt_image_tag="${UNIQUE_IDENTIFIER}" \
         -a ci_buildNumber="${KOKORO_BUILD_NUMBER}" \
-        -a ci_buildUrl= "https://source.cloud.google.com/results/invocations/" + "${KOKORO_BUILD_NUMBER}" \
+        -a ci_buildUrl="${CLOUD_LOGGING_URL}" \
         -a ci_jobName="${KOKORO_JOB_NAME}" \
         -a ci_gitCommit="${KOKORO_GIT_COMMIT}" \
         -a ci_gitActualCommit="${ghprbActualCommit}" \